1. Field of the Invention
Example embodiments relate to an integrated circuit device and a method of manufacturing the same, and more particularly, to an integrated circuit device including a resistor and a method of manufacturing the same.
2. Description of the Related Art
As the semiconductor industry has made rapid progress, integrated circuit devices have been utilized for many electronic instruments in various industrial fields. The integrated circuit device generally includes a great number of transistors, diodes, capacitors and resistors that are highly integrated therein, and thus an overall resistance of the integrated circuit device needs to be variable in accordance with requirements of the electronic instruments including the integrated circuit device.
In conventional integrated circuit devices, the resistor has an electric resistance greater than that of wiring structures and thus low-resistive materials for the wiring structure are insufficient for the resistor. In addition, the resistors are generally formed simultaneously with the diodes and the transistors and no additional process is provided just for the resistors in view of process efficiency of the manufacturing process.
For those reasons, the resistor of the integrated circuit devices may be formed on the device isolation layer simultaneously with the gate structure of the transistor. That is, the gate structure may be formed on an active region of a substrate and the transistor may be formed on the device isolation layer simultaneously with the gate structure in the same process. Since electric resistance of polysilicon is easily controlled by doping various impurities, both of the gate structure and the resistor generally include polysilicon.
A doped polysilicon pattern is usually used as the resistor of the integrated circuit device and a conductive connector is connected with the resistor and external wirings. Thus, the connector comprises low-resistive metals so as to reduce contact resistance at a boundary area of the resistor and the connector.
However, when polysilicon of the resistor and the metal of the connector make direct contact with each other, a plurality of voids is generated at the boundary area of the connector and the resistor due to the silicidation process of the polysilicon and the metal. Thus, a contact resistance of the resistor is rapidly increased and the resistor and the wiring tend to be electrically disconnected from each other due to the voids. Since it is widely known that the contact resistance has a critical effect on an overall sheet resistance of the resistor, the variation of the contact resistance caused by the silicidation between the resistor and the connector necessarily leads to the variation of the overall resistance of the resistor.
When programming, erasing or reading data in flash memory devices, a reference voltage is usually applied to a reference cell transistor by a reference cell operator and the reference cell operator conventionally needs the resistor. Thus, the large resistance variation of the resistor necessarily leads to an unstable operation of the reference cell operator, thereby severely deteriorating the reliability of the flash memory device. Recently, the resistance variation of the resistor is tend to increase due to the reduction of critical dimension (CD) of semiconductor chips and thus the operation reliability of the integrated circuit devices is tend to be deteriorated.
Accordingly, there is still a need for an improved resistor for integrated circuit devices in which the variation of the contact resistance and the sheet resistance are minimized and thus the operation reliability of the integrated circuit device is sufficiently improved.